I. Field of the Invention
This invention relates generally to coloration guides for use in dentistry. More particularly, this invention relates to improvements in dental shade guides for use by dentists and dental laboratory technicians. Dental shade guides are used to compare the coloration and shading of artificial teeth for accurate matching with a patient's natural teeth shade and color. The present invention provides a novel dental shade guide which uses the same or similar materials which are used to fabricate dental crowns, artificial teeth or other dental prostheses.
II. Description of the Prior Art
Dental shade guides are an important part of the dental field as a means of communicating a color of a patient's natural teeth from dentist to dental laboratory technician.
Conventional shade guides consist of artificial teeth that are mounted on one end of an individual arm or bar that is marked for that particular shade and then inserted into a plastic holder indicating that shade. This technique can create problems by the fact that the indivual arms or bars can become loose and fall out of the holder and become misplaced.
The artificial teeth of the dental shade guides are almost always manufactured out of a different type of porcelain than the dental glass used to fabricate crowns or bridges, and are fired in a kiln at a much higher temperature than the dental glass to achieve their color.
The thickness of the artificial teeth also causes a problem. The artificial teeth of dental shade guides are 3.5 to 4 millimeters thick and have no metal backing behind them. The dental laboratory technician has to construct a metal frame over a prepared tooth or teeth with a layer of opaque and then a layer of dental glass fired onto the metal all in a confined space of 2 millimeters or less in most cases.
The lack of a metal backing on the conventional dental shade guides renders the color and shade matching with the patient's natural teeth very difficult and often inaccurate. The crown or bridge which will ultimately replace the patient's natural teeth consists of an underlying metal framework covered with opaque. Dental glass is then fired onto the metal thereby creating an oxide layer between the metal and opaque. The artificial tooth having the metal framework, opaque, dental glass and oxide matrix reflects incoming light rather that transmitting it through the tooth as occurs with the non-metal backed artificial teeth of conventional shade guides. This property of light transmission or reflection alters the color and shade of the tooth. Therefore, the shade of an artificial tooth without a metal backing will differ from the shade of and artificial tooth having a metal backing. It is apparent, therefore, that a dental shade guide having a metal backing more accurately represents the true coloration and shading of the artificial teeth, crowns or bridges actually placed in a patient's mouth.
Known prior art examples of dental shade guides are disclosed in U.S. Pat. Nos. 1,518,608; 2,805,478; 3,964,167; and 785,992. These patents exhibit different dental shade guides which are revelant to applicant's invention. Each of these dental shade guides has deficiencies of the types aforementioned in that they do not provide the dentist or dental laboratory technician with a realistic dental shade guide to be used to compare artificial teeth to a patient's natural teeth for color as accurately as possible.